Reference indices
If your Belgian mortgage has a variable rate, it moves with one official index. Which index applies is fixed by law and follows from how often your rate is revised.
Values from our series, last checked on 2026-09-10.
| Index | Revision | Derived from | Latest value | Δ 12 mo |
|---|---|---|---|---|
| Index A | Every 1 years | Treasury certificates at 1 year | 1.950% | -1.245 |
| Index B | Every 2 years | Linear bonds (OLO) at 2 years | 2.040% | -0.842 |
| Index C | Every 3 years | Linear bonds (OLO) at 3 years | 2.163% | -0.494 |
| Index D | Every 4 years | Linear bonds (OLO) at 4 years | 2.340% | -0.251 |
| Index E | Every 5 years | Linear bonds (OLO) at 5 years | 2.527% | -0.101 |
| Index F | Every 6 years | Linear bonds (OLO) at 6 years | 2.692% | +0.014 |
| Index G | Every 7 years | Linear bonds (OLO) at 7 years | 2.839% | +0.105 |
| Index H | Every 8 years | Linear bonds (OLO) at 8 years | 2.975% | +0.178 |
| Index I | Every 9 years | Linear bonds (OLO) at 9 years | 3.101% | +0.236 |
| Index J | Every 10 years | Linear bonds (OLO) at 10 years | 3.220% | +0.285 |
Historical indices for variable mortgage rates (source: FPS Economy)
Latest values (Aug 2025)
Index A
1.950%
Index B
2.040%
Index C
2.163%
Index D
2.340%
Index E
2.527%
Index F
2.692%
Index G
2.839%
Index H
2.975%
Index I
3.101%
Index J
3.220%
A reference index is an official figure set monthly by the Federal Debt Agency as the arithmetic mean of theoretical yields on Belgian government paper. It is published in the Belgisch Staatsblad on the twentieth of each month. Banks may only move your variable rate against such an index, never against an internal rate of their own.
It follows from the revision period in your contract. A rate revised yearly is tied to index A; every three years to index C; every five years to index E; every ten years to index J. And so on for each period from one to ten years. Your credit deed states both the index and its initial value.
Belgian law caps movement in both directions. Your rate can never more than double over the life of the loan relative to the starting rate. On top of that, the rate in year two may exceed year one by at most 1 percentage point, and year three by at most 2 points over the start. Borrow at 2% and you never pay more than 4%, even if the market reaches 7%.
At signing the bank fixes the index value that serves as the starting point: the value for the calendar month before the date of the rate sheet your offer is based on. At each revision the new index value is compared with that starting value, and the difference is applied to your rate. Your margin above the index stays unchanged.
The FPS Economy publishes the monthly list of all indices on its website, and the Federal Debt Agency publishes the underlying prices daily. The series below runs from November 1992 and is what our comparison tool uses to project variable formulas.
Received an offer with a variable rate? Our tool projects the scenario and puts it next to the fixed formulas.
Compare your offersSource: FPS Economy, reference indices for variable rates on mortgage credit (art. VII.143 Code of Economic Law, Royal Decree of 14 September 2016). Our series is indicative; always consult the official publication for binding values.
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